• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.71-81
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• 2005

Surface wave techniques were initially based on 2-D plane waves and were later improved to the techniques based the 3-D based cylindrical waves. However, body-wave interference, near-field effect and limited technology in surface wave measurements restricted the use of 3-D cylindrical waves to the 1-D evaluation of subgrade stiffness. In this study, by the numerical simulation of SASW measurements, the dispersion properties of surface waves including vertical, horizontal Rayleigh waves and Love waves were thoroughly investigated in the 3-D domain, and a new filter criteria to minimize the near-field effect was established, which led to CAP (common-array-profiling)-SASW technique. The CAP-SASW technique enabled the evaluation of subgrade stiffness fur a specific subgrade segment, not for a whole section of measurement array. Therefore, a contour plot of subgrade stiffness with a ground-truth quality can be obtained by the CAP-SASW technique. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.477-485
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• 2018

To control manage environmental load during construction work, it is required to ascertain an accurate quantity for materials those are using during the construction. In construction industrial nowadays, especially on design part, there are lots of mistakes occurred on quantity take-off between plan documents and actual work. That mistakes are caused by omission of design items, overcount because of interference each materials or simple calculate error. Besides, in case of a construction project, engineers are impossible to design perfectly due to a lot of invalid variable in a construction site. Thus, design errors and changes occur frequently in the process of construction work or design due to such unclear elements. And in case of LCA assessment based on 2D design, there is difficult for an engineer who is in charge to calculate the volume of materials manually using drawings and relevant specifications. This study is aimed for examining and verifying a high reliable method of evaluating environmental load which is useful in construction process through comparing LCA analysis. In addition, this study provides the method of calculating the volume of materials and LCA assessment in working on the basis of 2D design, using the specifications which is used for LCA evaluation, and possibility of utilizing the LCA assessment by introducing BIM design technic to improve the former problem through comparing and analyzing the previous method with 3D-based evaluation process.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.2
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• pp.149-158
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• 1998

Biomass of non-living brown seaweed Sargassun fluitans pretreated with NaOH is capable of taking up more than $10\%$ $(q_{max}$ : 3.85 mmol/g for Al and 1.48 mmol/g for Cu) of its dry weight in the Al and Cu at pH of 4.5. However, the maximum Al and Cu uptakes calculated from Langmuir isotherm were 1.58 mmol/g for Al and 1.35 mmol/g for Cu at pH 3.5. Equilibrium batch sorption study was performed using two-metal system containing Al and Cu. The mathematical model of the two-metal sorption system enabled quantitative estimation of one-metal biosorption inhibition due to the influence of a second metal. NaOH-treated S. fluitans contained 2.19 mmol $(43\;wt.\%)$ carboxyl groups per gram of biomass. A modified form of Langmuir, which assumes binding of Cu as $Cu^{2+}$ and Al as $Al(OH)_2^+,$ was used to model the experimental data. This result agrees with the one of mono-valent sorption for Al in single-metal system. The modified Langmuir model gives the following affinity correlated coefficients: 0.196 for Cu and 6.820 for Ah at pH 4.5, and 2.904 for Cu and 3.131 for Al at pH 3.5. The interference of Al in Cu biosorptive uptake was assessed by `cutting' the three dimensional uptake isotherm surfaces at constant second-metal final concentrations. Equimolar final equilibrium concentrations of Cu and Al of 1 mM at pH 4.5 give Cu and hi uptakes reduced by $82.5\%\;and\;5.4\%,$ respectively. However, these values at pH 3.5 were $55\%\;(Cu)\;and\;31\%$ (Al).

• Journal of Korean Society of Forest Science
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• v.64 no.1
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• pp.64-73
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• 1984

As data basic to policy in nature conservation, the Degree of Green Naturality (DGN) survey was usually carried out. This also explains the impact of human interference to natural environment. Gongju gun and Yeongi gun were surveyed in the summer of 1983 to determine the DGN of these districts. Then, the surveyed DGN was compared to the existing standard. The results obtained appeared that the average DGN of these districts ranged about 5.1 to 5.9 and especially the ratio of DGN 7-graded area was high. Because of difficulties in applying the existing standard directly to middle part of Korea, further improvement on the existing standard for ranking or surveying the DGN should be reconsidered.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.19-22
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• 2017

In this study, wavelength-free $1{\times}N$ optical splitter using a tapered polymer waveguide was studied to realize the transmission network of high-speed information communication network. Based on the evaluation of mode converting characteristics of splitter having two tapered multi-mode interference structures, an optimized structure of the $1{\times}N$ splitter was proposed for wide-range of input wavelength. 2D-BPM analysis $1{\times}8$ model showed that insertion loss of the proposed splitter is less than 10 dB for wavelength of input source from 1260 nm to 1650 nm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.131-137
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• 2015

This paper relates with the VSS-MMA (Variable Step Size-Multiple Modulus Algorithm) adaptive equalization algorithm which is possible to improving the equalization performance by use the nonlinear fuction of error signal in the MMA adaptive equalization algorithm that are used for the minimization of the intersymbol interference due to the distortion which occurs in the time dispersive channel for the transmission of QAM signal in the system.. In the conventional MMA, we obtains the tap coefficient of adaptive equalizer using the fixed step size, but in the VSS-MMA, we obtains the tap coefficient of adaptive equalizer using the variable step size based on a nonlinear function of error signal. By adapting the variable step size, it was confirmed that the improved equalization performance were obtained by computer simulation. For this, the equalizer output signal constellation, residual isi, maximum distortion, MSE and SER were used in the performace index.

• The Korean Journal of Ecology
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• v.24 no.5
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• pp.323-332
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• 2001

A cultural landscape results from a combination of human activities for resource-use and the response of nature to such artificial interference. Nature provides resources necessary for human life on the Earth in terms of his survival as well as living. Humanbeing has developed civilization using the benefits that nature provides. In the past, a harmonious relationship between mankind and nature had ensured sustainability of resource-use for human. We can find such facts from the existence of cultural landscape. However, rapid economic growth and a development-oriented logic caused from such socio-economic change led to the environmental crises and the depletion of various resources at global level. In the perspective of preparation for such problems, we investigated the background for establishment, function, and value of cultural landscapes, in which a dynamic equilibrium exists between a supply of natural resources and human needs. Furthermore, we discussed a new economic model including ecological consideration, a strategy for ecological management of environment, and a framework for transmission of traditional culture to new generations on the basis of a cultural landscape regime.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.33-40
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• 2010

In this paper, the bit-error-ratio (BER) performances of Digital Radio Mondiale Plus (DRM+) system which stand for the European standard to bring analogue FM radio to digital radio in Band-II(30-170 MHz) are evaluated under multipath fading channel models used in Band-II and the adjacent channel interference (ACI) caused by FM signal. From the simulation results, the DRM+ system shows robust performances under time-varying channel environments even though the speed of a vehicle is equal to 300km/h. And it is shown that the frequency diversity, determined by delay spread of multipath fading channel, increases the coding gain of the DRM+ system with an increase of delay spread. In addition, to guarantee the BER performance of 10-4 for DRM+ system with ACI due to FM signal, the simulation results show that the desired signal-to-ACI power ratio must be more than -30 dB when the carrier frequency distance is 150 kHz.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.269-273
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• 2013

Underwater acoustic channels are generally recognized as one of the most difficult communication media because of the multipath propagation, dispersion, and so on. MIMO (Multiple-input multiple-output) techniques have been actively pursued in underwater acoustic communications recently to increase the data rate over the bandwidth-limited channels. The transmit diversity techniques can be applied in this case, and one of them is Alamouti's scheme. In this paper the performances of the transmit diversity technique are evaluated via experiment. Two transmitters and two receivers were used in experiment, and the experiment was performed in indoor water tank. The error rate 5~8% was confirmed in experimental results, and these are the improved values than the error rate 14.8% for SISO(Single-input single-output) channel under same data rate condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.294-301
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• 2013

OFDM technique uses multiple sub-carriers for the data transmission. Therefore, bit error rate increases because of inter-carrier interference caused by nonlinear high power amplifier and carrier frequency offset. Wireless OFDM transmission over multi path fading channels is characterized by small transmission gain in multiple sub-carrier frequency interval. Therefore bit error rate increases because of burst errors. Inter-leaver and convolution error control coding are effective for the reduction of this burst error. Pilot symbol is used for the channel estimation in OFDM systems. However, imperfect channel estimates in this systems degrade the performance. The performance of this convolution coding OFDM systems using inter-leaver, gauged by the bit error rate, is analyzed considering the nonlinear high power amplifier, carrier frequency offset and channel estimation error.